Japanese National Patent Publication Gazette No. 2005-529574 discloses an electrostatic operation device (electrostatic induction power generating device) comprising an electret film is known. This electrostatic induction power generating device disclosed in Japanese National Patent Publication Gazette No. 2005-529574 is constituted by a movable electrode, a fixed electrode and an electret film made of a charge holding material of a resin material such as Teflon (registered trademark) formed on the fixed electrode. In this electrostatic induction power generating device, the movable electrode repeatedly vibrates by receiving inertial force, so that electric charges induced in the movable electrode with electric charges stored in the electret film are changed to output the changed amount of electric charges as a current.
In the aforementioned electrostatic induction power generating device employing the electret film, however, the electrostatic induction power generating device receives a physical impact and the movable electrode and the electret film come into physical contact with each other, whereby the amount of electric charges stored in the electret film is disadvantageously changed.